It is known that polymeric materials must be pretreated before the chemical metallisation and the subsequent electroplating, for example by etching of the polymer surface with chromic and sulphuric acids, which pollute the environment.
EP-A 0,081,129 has also disclosed that an activation, which is obtained by "swelling adhesion activation", leads to well adhering metal deposits. This elegant process has the disadvantage, however, that it causes stress cracking in the case of polymer injection-mouldings of complicated shape. Moreover, this process requires a new swelling activation system for each type of plastic and is thus not universally applicable.
U.S. Pat. No. 3,560,257, U.S. Pat. No. 4,368,281 and U.S. Pat. No. 4,017,265and DE-A 3,627,256 and 2,443,488 have disclosed processes for activation, which use activator solutions which contain adhesion-promoting polymers. The disadvantage of these processes is that they require the use of relatively large quantities of expensive noble metal activators. Moreover, they succeed as desired only in the case of very specific plastics and are therefore also applicable only with restrictions.
For this reason, Pd-containing primers are proposed in EP-A 0,361,754, which require the additional use of chromic and sulphuric acids. Pd-containing primers based on PU (polyurethane) are also known from DE-A 3,627,256. The disadvantage of these elegant processes is that they cause stress cracking of plastic injection-mouldings of complicated shape.
Finally, special adhesion-promoting plastic coatings can be taken from DE-A 3,814,506, but these lead in some cases to extraneous deposition depending on the geometry.